Electrical penetrant structure

ABSTRACT

An electrical penetrant structure, and a method of making the same, are disclosed for feeding sealingly one or more electrical conductors through a wall, such as the containment vessel wall in a nuclear-powered electrical generating station. The penetrant structure comprises a tubular metal housing through which a metal conductor extends noncentrally but in spaced relation to the surrounding housing wall surface, such surface being annularly recessed ro provide an enlarged chamber filled with resilient insulating material in compression and surrounding a laterally offset portion of said conductor. The method for making such structure involves swagging an assembly of the housing having an external groove therein surrounding a body of insulating material having a noncentral hole through which the conductor extends, this swagging causing the insulating material to be compressed between the housing and conductor and the portion of the conductor adjacent the groove to become laterally offset while embedded in the insulating material.

United States Patent [72] Inventors Frederick G. Bohne Buffalo; Mark 0.Johnson, Grand Island, both of, N.Y. t [21] Appl. No. 748,715 [22] FiledJuly 30, 1968 [45] Patented Aug. 24, 1971 [73) Assignee ConaxCorporation Buffalo, N.Y.

[54} ELECTRICAL PENET RANT STRUCTURE 3 Claims, 12 Drawing Figs.

[52] US. Cl 174/151, 29/517, 29/624, 29/629, 174/11 R, 174/23 R, 174/65SS, 174/77 R [51] Int. Cl ..H01b 17/26 [50] Field of Search. 174/11 R,18, 23 R,77 R, 65 R, 65 SS, 151

[56] References Cited UNITED STATES PATENTS 452,342 5/1891 Conner 174/233,055,972 9/1962 Peterson... 174/65 (.1) X

Primary ExaminerLaramie E. Askin Attorney-Sommer, Weber & GastelABSTRACT: An electrical penetrant structure, and a method of making thesame, are disclosed for feeding sealingly one or more electricalconductors through a wall, such as the containment vessel wall in anuclear-powered electrical generating station. The penetrant structurecomprises a tubular metal housing through which a metal conductorextends noncentrally but in spaced relation to the surrounding housingwall surface, such surface being annularly recessed ro provide anenlarged chamber filled with resilient insulating material incompression and surrounding a laterally offset portion of saidconductor. The method for making such structure involves swagging anassembly of the housing having an external groove therein surrounding abody of insulating material having a noncentral hole through which theconductor extends, this swagging causing the insulating material to becompressed between the housing and conductor and the portion of theconductor adjacent the groove to become laterally offset while embeddedin the insulating material.

PmENwEMus-mfl 8.601. 526

SHEET 1 OF 3 /Fig. 3.

f Fig. 4.

33 40 3lo 4o 37 26c 3 2O 2lo 22/o 2230 1 3 38 Z I! I IN VENT )RSFrederick .Bohne Mo K O. nson ATTORNEYS r 4 WW ELECTRICAL PENETRANTSTRUCTURE BACKGROUND OF THE INVENTION There are environments in which itis desirable to feed an electrical conductor through a wall so that theconductor is not only insulated from the wall but also penetrates thewall in a sealed manner so that fluids on one side of the wall cannotescape through the electrical penetrant structure. This presentsproblems in effectively sealing the conductor, as well as mounting thesame on the wall which it penetrates. The present invention is addressedto a solution of these problems.

SUMMARY OF THE INVENTION The electrical penetrant structure of thepresent invention comprises an elongated metal tubular member whichpenetrates the wall and houses a body of compressed resilient insulatingmaterial with one or more electrical conductors extending through suchbody. Swaging is employed to unitize a loose assembly of housing,insulating bodies and conductor elements to provide the final electricalpenetrant structure. The housing is externally grooved before swaging soas to provide after swaging an internal contoured sealing chamber intowhich the insulating material is forced, and to cause any noncentralconductor to be laterally offset at such chamber, thereby to lock thevarious elements together mechanically while forcing them into sealingengagement with one another.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary longitudinalsectional view through a loose assembly of housing, insulating body andconductor elements prior to swaging in accordance with the presentinvention.

FIG. 2 is a view similar generally to FIG. 1 but depicts the conditionof the assembly after being substantially fully swaged from end to end,thereby to illustrate the final construction of the electrical penetrantstructure which represents one form of the present invention.

FIG. 3 is an enlarged fragmentary portion of the section shown in FIG. 1taken near the right end thereof.

FIG. 4 is an enlarged fragmentary portion of the section shown in FIG. 2taken near the right end thereof.

FIG. 5 is an enlarged transverse sectional view of the assembly shown inFIG. 1 and before swaging taken on line 5-5 thereof.

FIG. 6 is an enlarged transverse sectional view of the final electricalpenetrant structure after swaging, this view being taken on line 66 ofFIG. 2.

FIG. 7 is a longitudinal sectional view through one means for mountingon a wall the form of inventive electrical penetrant structure shown inFIGS. 1-6.

FIG. 8 illustrates another technique of mounting on spaced walls amodified form of electrical penetrant structure made in accordance withthe present invention.

FIG. 9 is an enlarged fragmentary longitudinal view, principally incentral section, of the modified form of electrical penetrant structureshown in FIG. 8.

FIG. 10 depicts an elongated metal tubular housing member which willultimately form an element of still another form of inventive electricalpenetrant structure and showing such member welded to a mounting bracketprior to association with the other elements of the penetrant structure.

FIG. 11 shows the housing member just referred to loosely assembled withan insulating body and conductor elements, prior to swaging.

FIG. 12 depicts the assembly after swaging and illustrates the finalconstruction of this form of electrical penetrant structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS There are three preferredembodiments of electrical penetrant structure illustrated in theaccompanying drawings.

Each will be described under separate subheadings of the Figures of thedrawings which illustrate the corresponding form of electrical penetrantstructure. Accordingly, the first preferred form of the invention willbe described in connection with FIGS. 1-7; the second form in connectionwith FIGS.

8 and 9; and the third form in connection with FIGS. 10-12.

FIGS. 1-7

The numeral 20 represents generally an elongated tubular metal housing.It is preferably cylindrical in cross section throughout its length. Asshown in FIG. 1, this housing has a cylindrical bore 21 of uniformdiameter from end to end. The housing also has an external periphery 22concentric to bore 21 and which is uniform from end to end except for aninterruption adjacent each end which will now be described.

Adjacent each end, housing 20 is shown as provided with an externalannular groove 23 for purposes which will be explained later. Eachgroove 23 must have a radial depth at least equal to one quarter of thewall thickness of housing 20. Also, each groove 23 must have an axiallength before swaging as hereinafter explained which is at least equalto the radius of the external diameter of the ungrooved portion of thehousing 20 before swaging. Still further, the outer radial end wall 24of each groove 23 must be arranged axially inwardly from the adjacentouter end face 25 of housing 20 a distance at least equal to the outsidediameter of peripheral surface 22 of the housing 20 prior to swaging.This housing 20 may be made of any suitable metal or metal alloy such asstainless steel.

Referring to FIG. 1, arranged symmetrically within tubular housing 20 isan elongated cylindrical body of resilient insulating materialrepresented generally by the numeral 26. The external periphery 28 ofinsulating body 26 is cylindrical and spaced slightly from the opposinginternal cylindrical surface 21 of surrounding housing 20. Typically theclearance between opposing surfaces 21 and 28 is 0.0025 to 0.003 inch.Body 26 is shown as having an axial length greater than that of housing20 so that a portion of the body extends outwardly beyond end face 25 ateach end of the housing, each such extension being indicated at 29. Theinsulating body 26 may be an suitable thermoplastic such astetrafluoroethylene, elastomer such as rubber or neoprene, or epoxyresin.

As shown in FIG. 5, insulating body 26 has a series of fivesymmetrically arranged through holes severally adapted to receiveconductors. One such hole is centrally arranged and extends coaxially ofcylindrical body 26 and is designated 30. At equidistant circumferentialintervals and at a uniform spacing radially between the axial centerlineof cylindrical body 26 and its cylindrical periphery 28 are the fourremaining through holes typically represented by the numeral 31. All theholes 30 and 31 extend generally parallel to one another.

As stated, a conductor is arranged in each such hole 30 and 31. Thecentral conductor is represented by the numeral 32 and typically theconductor in each of the other holes 31 is represented by the numeral33. The central conductor 32 and the noncentral conductors 33 are eachmade of a suitable solid metal or combination of metals so as to providean incompressible wire capable of withstanding the radial pressuresexerted during the swaging operation as explained later herein. Theseconductors may be made of any metal, or combinations of metal, such ascopper, nickel or a thermocouple element such as iron-constantan orchromel-alumel.

The conductors 32 and 33 are preferably in the form .of cylindricalwires and may be coated or uncoated with a sleeve of insulatingmaterial. As shown, each of the conductors 32 and 33 is preferablyencased in a sleeve 27 of suitable insulating material. The conductors32 and 33 are of a length greater than that of the body of insulatingmaterial 26. The ends of these conductors are adapted to be connected toother leads or conductors in any suitable manner, no such connectionbeing illustrated since it forms no part of the present invention.

The conductors 32 and 33 are placed within their respective holes 30 and31 in the body 26 of insulating material. To permit of this, a slightclearance between the opposing surfaces is provided, this clearance alsobeing in the order of 0.0025 to 0.003 inch.

From the foregoing, it will be seen that the housing 20, insulating body26 and conductor elements 32 and 33 can be readily assembled to providethe loose assembly depicted in FIG. I. Thereafter this loose assembly isswaged in a conventional swaging machine having swaging dies typicallyillustrated at 34 and 35 in FIG. 2. As is well known, the item to beswaged, here specifically the loose assembly of housing 20, insulatingbody 26 and conductors 32 and 33, is fed axially through the openingformed by the swaging dies 34 and 35. Suitable drive means (not shown)cause these dies to move toward each other and in the process the looseassembly is radially compressed to a smaller diameter than it had asdepicted in FIG. 1. Referring to FIG. 2, the slightly more than righthalf of the electrical penetrant structure depicted therein has beenswaged whereas the left-hand portion of the assembly shown surrounded bythe swaging dies 34 and 35 has not as yet been swaged.

Referring to FIGS. 2 and 4, it will be seen that as a result of theswaging operation the wall section of metal housing 20 formed underannular groove 23 is offset outwardly with respect to the adjacent wallportions of this housing. As shown in FIG. 4, this offset wall section23a has an external surface 36 which is coterminous with the adjacentexternal periphery 22a of the tubular housing at opposite ends of wallsection 23a. The external surface, in other words, has substantially thesame diameter over the portions of the housing which had been providedwith grooves 23 as compared with the portions of the housing unprovidedwith such grooves. After swaging, the exterior of housing 20 wheregroove 23 had been is detectable only by the annular slanted V-shapedgrooves typically indicated at 38, one at each end of where the end wallof groove 23 had been.

Offset wall section 23a has an internal surface 39 which is offsetradially outwardly with respect to the final internal wall surface 21aof housing 20. In other words, the diameter of internal annular wallsurface 39 is greater than that of annular internal wall surface 21a.The transition from the diameter of wall surface 21a to that of wallsurface 39 is gradual as indicated at 40 at each end of wall section23a. The portion of the interior of housing 20 after swaging defined bytransitional end portions 40 and intermediate enlarged wall surface 39provide a contoured chamber or enlarged chamber into which as a resultof the swaging operation a portion of body 26 extends to transverselyfill and seal this chamber.

It is pointed out that as a result of the swaging operation all of theclearances that had existed between the housing 20 and insulating body26 and also between the latter and the various conductors 32 and 33,have been eliminated. In fact, the original insulating body 26 has beencompressed radially between the end limits 25 of housing 20 into a newbody designated 26a which is in a state of compression and firmly andsealingly engages the internal surface of the housing and the variousconductors 32 and 33 which this body surrounds. More specifically, thecentral conductor 32 is sealingly grasped by body 26a. In the case ofthe satellite conductors 31, each has a laterally offset portion 31awhich is offset radially outwardly toward wall surface 39 of thehousing. The effect of this offset is to mechanically interlockconductors 32 to insulating body 26a. As previously noted, thetransverse filling of the enlarged internal chamber formed by surfaces39 and 40 serves to interlock insulating body 260 to housing 20. Notonly does there exist this mechanical interlocking, but as well theinsulating body 26a is firmly compacted against the internal surfaces210, 40 and 39 of metal housing 20 and also against the externalsurfaces of conductors 32 and 33.

The amount of reduction in gross diameter of the electrical penetrantstructure after swaging as compared to before swaging coupled with theinitial clearances referred to between the opposing surfaces of thethree types of elements, namely conductors, insulating body and metalhousing, are such as to produce at least a percent reduction in thecross-sectional area of the insulating body. In other words, at a crosssection where a groove 23 has been, the cross-sectional area ofinsulating body 26 before swaging has been reduced at least 10 percentafter swaging to form body 26a.

Referring to FIGS. 1 and 2, it will be noted that an internal contouredsealing chamber is provided adjacent each end of the electricalpenetrant structure to prevent leaks axially through this structureeither along the interface between the insulating body and thesurrounding metal housing or along the interface between the variousconductors which extend through the insulating body.

Referring to FIG. 2, it will be noted that after swaging the portion 29awhich extends axially outwardly of the adjacent end of the metal housinghas an uncompressed condition as compared to that portion of the bodyconfined within the metal housing 20 and reduced in cross-sectional areaas a result of the swaging operation. This provides a slight offsettingas indicated at 37 of the satellite conductors 33 and also provides agradually enlarging clearance for the end portions of the wires as theyleave the insulating body and protects these wires against sharp bendingadjacent metal housing 20.

Referring to FIG. 7, a suggested type of mounting is disclosed for theswaged electrical penetrant structure just described which in that FIG.is represented generally by the numeral 41. As indicated hereinabove,the purpose of the electrical penetrant structure is to feed theconductors in a sealed and insulated manner through a wall. In FIG. 7such wall is indicated at 42. It is shown as having an internallythreaded hole 43 which receives the externally threaded nipple of agland body 44. This gland body is shown as having an internal throughbore 45 through which electrical penetrant structure 41 extends. Theouter end portion of this bore 45 is shown enlarged to accommodate asealing body 46 backed up by a gland follower 48. A cap 49 threadedlyconnected to gland body 44 enables pressure to be applied to glandfollower 48 and compress sealant 46 so as to sealingly engage and firmlygrip the external surface of electrical penetrant structure 41. Thearrangement shown in FIG. 7 is merely suggestive. Any other suitablemeans or mode of mounting the electrical penetrant structure 41 may beemployed.

FIG. 9 illustrates a construction of electrical penetrant structureembodying a modified form of the invention. Referring to this FIG., theinventive structure represented generally by the numeral 50 includes ametal housing 51, a body of resilient insulating material 52 arranged atthe left end of this housing, a central conductor 53 and a plurality ofuniformly spaced satellite conductors 54 extending though thisinsulating body. The body 52 of insulating material does not extendcompletely through the metal housing 51. A separate body 55 ofinsulating material is arranged internally of housing 51 adjacent theright end portion of this housing. The opposing end faces of insulatingbodies 52 and 55 are axially spaced from each other to provide aninternal space 56 within housing 51. Communication to the outside ofthis housing from this space is provided by a hole 57 in housing 51,provided therein prior to swaging. The purpose of this hole is to allowthe introduction of pressurized gas into space 56 to test for leakage ofthe electrical penetrant structure 50.

It will also be noted that the right end portion of electrical penetrantstructure 50 as shown in FIG. 9 is provided with two contoured sealingchambers, an outer one indicated at 58 and an inner one indicated at 59.The left end portion of the electrical penetrant structure 50 has onlyone contoured sealing chamber indicated at 60. Except for thedifferences noted, the construction and manufacture method of themodified form of electrical penetrant structure 50 shown in FIG. 9 issimilar to that shown in FIGS. 1-7.

FIG. 8 illustrates a manner of mounting electrical penetrantstructure-50 on a wall 61. This wall is shown as having a cylindricalopening 62 in which a cylindrical metal pipe 63 is arranged and thispipe is shown as sealed to the outer metal plates 64 of wall 61 byhaving a welded connection indicated at 65 which extends annularly ofhole 62. An end wall in the form of a plate 66 of circular outline isarranged opposite the left end of pipe 63, an O-ring 67 being interposedtherebetween for sealing purposes. An end cap 68 clamps end wall 66against pipe 63. At the opposite end of the structure a second end wall69 is arranged against the right end face of pipe 63 with an O-ring 70being interposed therebetween. A cap 71 clamps end wall 69 against pipe63.

End wall 66 is shown as having a packing gland fitting representedgenerally by the numeral 72 which is similar in detailed construction tothat described in connection with FIG. 7. This fitting sealingly mountsthe left end portion of electrical penetrant structure 50 on left endwall 66, the fitting having a threaded connection with this end wall. Atthe right end of electrical penetrant structure 50, another packinggland fitting 73 similar to the one indicated at 72 mounts the right endportion of electrical penetrant structure 50 on end wall 69, thisfitting 73 having a threaded mounting on this end wall. It will be notedthat the hole 57 in electrical penetrant structure 50 communicates withthe chamber 74 defined by pipe 63 and end walls 66 and 69. A pressurizedtest gas can be admitted to this chamber 74 to be forced into space 56in the electrical penetrant structure 50 and detection is then attemptedof this gas if it escapes axially outwardly along structure 50. For thepurpose of admitting the text gas into space 74, left end wall 66 isshown as provided with an access hole 75.

FIGS. -12

The electrical penetrant structure represented generally by the numeral76 is a third form of the invention and is depicted in its final form inFIG. 12. This structure 76 is characterized by having an attachingbracket 77 welded to the metal housing 78 to permit of mounting theelectrical penetrant structure on some suitable support (not shown).Inasmuch as the welding operation could distort the electrical penetrantstructure if performed after this structure was in its final formfollowing swaging, it is desirable to attach the mounting bracket 77shown in FIG. 10 to metal housing 78 prior to even a loose assembly ofthis housing with a body 79 of insulating material and a centralconductor 80 and a series of satellite conductors 81, all as shown inFIG. 11.

Returning to FIG. 10, it will be noted that housing 78 is similar tohousing shown in FIG. 1 except that prior to the assembly of theinsulating body and the conductors therewithin the mounting bracket 77is annularly welded as indicated at 82 and 83 to the exterior of thismetal housing.

After mounting bracket 77 has been so welded to metal housing 78, theinsulating body 79 and the conductors 80 and 81 are assembled looselywith housing 78, as depicted in FIG. 11. But for the preattachment ofmounting bracket 77 to metal housing 78, the loose assembly of elementsdepicted in FIG. 1 1 corresponds to the loose assembly of similarelements depicted in FIG. 1.

Thereafter the loose assembly shown in FIG. 11 is swaged longitudinallyfrom each end of the assembly toward the center or toward the mountingbracket 77. This results in the final electrical penetrant structure 76depicted in FIG. 12. Referring to such FIG., the left end portion 84including the contoured sealing chamber 85 has been swaged, and also theright end portion 86 of the assembly including a contoured sealingchamber 87 has been swaged. This leaves an intermediate unswaged portion88 immediately under and adjacent mounting bracket 77. The electricalpenetrant structure structure 76 may be mounted to a supporting wall(not shown) by securing suitable mounting bracket 77 thereto.

From the foregoing, it will be seen that each of the three preferredforms of the invention illustrated and described includes at least oneinternal contoured sealing chamber adjacent each end of the electricalpenetrant structure. An additional contoured sealing chamber can beprovided such as in the case of the form of the invention shown in FIG.9, for additional sealing if desired. It will also be noted that theresilient insulating material can be continuous from end to end of themetal housing, as in the case of the forms of the invention shown inFIGS. 1-7 and 10-12, or can be interrupted to leave an intermediate gaspressurizing space as in the case of the form of the invention shown inFIGS. 8 and 9.

It will be further noted that in each form of the invention disclosedthe body of insulating material extendsaxially outwardly of the end ofthe metal housing to provide protection for the wires or conductors asthey leave the electrical penetrant structure.

The invention is adaptable to an electrical penetrant structure havingone or more conductors. The number of conductors illustrated is notlimitative of the invention in this regard. As previously indicated,these conductors can be insulated or not. However, the conductors shouldbe incompressible metal conductors so that no voids will be presentafter the swaging operation.

It is has been found in actual practice that an electrical penetrantstructure constructed in accordance with the principles of the presentinvention is highly effective in permitting one or more electricalconductors to be fed through a wall in such a manner that a sealed andinsulated penetration of this wall is provided. The inventive electricalpenetrant structure is particularly advantageous for penetrating thecontainment vessel wall in a nuclear-powered electrical generatingstation.

We claim:

1. An electrical penetrant structure, comprising an elongated tubularmetal housing, at least one incompressible metal conductor extendingthrough said housing in spaced relation to the surrounding internal wallsurface thereof, a portion of said wall surface adjacent each end ofsaid housing being annularly recessed to provide a transversely enlargedinternal chamber adjacent each end of said housing, the axial length ofeach such recessed wall surface portion being at least equal to half thetransverse dimension of the exterior of said housing, the outer edge ofeach of said portions being arranged axially inwardly from the adjacentouter end of said housing a distance at least equal to said transversedimension, and resilient insulating material compressed between saidhousing and conductor and transversely filling and axially extendingbeyond the ends of each of such chambers, said conductor beingnoncentrally arranged in said insulating material and the portion ofsaid conductor passing through each chamber being laterally offsettoward the corresponding recessed wall surface portion.

2. An electrical penetrant structure according to claim 1, wherein saidinsulating material extends axially outwardly beyond each outer end ofsaid housing.

3. An electrical penetrant structure according to claim 2, whereinaxially separated bodies of said insulating material are arranged withinsaid housing to provide a space therebetween, and said housing has ahole in the wall thereof communicating with said space.

1. An electrical penetrant structure, comprising an elongAted tubularmetal housing, at least one incompressible metal conductor extendingthrough said housing in spaced relation to the surrounding internal wallsurface thereof, a portion of said wall surface adjacent each end ofsaid housing being annularly recessed to provide a transversely enlargedinternal chamber adjacent each end of said housing, the axial length ofeach such recessed wall surface portion being at least equal to half thetransverse dimension of the exterior of said housing, the outer edge ofeach of said portions being arranged axially inwardly from the adjacentouter end of said housing a distance at least equal to said transversedimension, and resilient insulating material compressed between saidhousing and conductor and transversely filling and axially extendingbeyond the ends of each of such chambers, said conductor beingnoncentrally arranged in said insulating material and the portion ofsaid conductor passing through each chamber being laterally offsettoward the corresponding recessed wall surface portion.
 2. An electricalpenetrant structure according to claim 1, wherein said insulatingmaterial extends axially outwardly beyond each outer end of saidhousing.
 3. An electrical penetrant structure according to claim 2,wherein axially separated bodies of said insulating material arearranged within said housing to provide a space therebetween, and saidhousing has a hole in the wall thereof communicating with said space.